Tube cooling means



June 9, 1942. J. A. HUTCHESON TUBE COOLING MEANS Filed s t. 19, 1940 III] INVENTOR J07? /7 Hu/cheson. I

WITNESSES:

Afrou Patented June 9, 1942 TUBE COOLING n John A. Hutcheson, Caton sville, Md., assignor to 7 Westinghouse Electric 8; Manufacturing-Company, East Pittsburgh, Pa.,' acorporation of Pennsylvania Application September 19, 1940, Serial No. 357,355

Claims.

My invention relates to electrical discharge tubes and circuits therefor, and in particular to tubes and circuits of this type which are designed to operate at extremely high frequencies.

One object of my invention is to provide an arrangement for efiiciently cooling the anode of an electrical discharge device.

Another object of my invention is to provide a structure for supporting an electrical discharge device and for efficiently connecting it to an oscillation circuit of the concentric line type.

Another object of my invention is to provide a structure which performs the combined functions of efficiently cooling the anode of an electrical discharge device while coupling it for efficient operation in conjunction with an oscillation circuit of the concentric line type.

Still'another object of my invention is to provide an electrical discharge device adapted to act as an oscillator, amplifier or'detector of radio currents of extremely high frequencies with a composite structure which'performs thefunctions of supporting the discharge tube efliciently cooling its anode and providing a tunable oscillation-circuit of the concentric line type which is so coupled to the discharge tube as to permit efficient operation in conjunction therewith. I

Other objects of. 'my invention will become apparent on reading the following specification to; amplify, oscillate or detect alternating currents of extremely high frequencies, such, for example, as those radiating waves having a length of the order of one meter" usually have relatively small physical dimensions; and, where they are to transmit even moderate amounts of power, a problem arises in attaining efiicient dissipation of the heat set free at their anodes. One typical tube of the type just discussed has an anode comprising a copper shell forming a portionof the tube Wall, the control electrode and cathode being positioned in the interior of this shell and sealed thereto by a glass wall portion positioned at one end of the copper shell. The anode shell constitutes a major portion of the side walls and also forms one end of the tube, and the cathode and grid leads project from this glass wall portion atthe other end of tbetube; v

In accordance'with the prior art, radial vanes of considerable dimensions were attached to the copper anode shell for the purpose of dissipating the heat set free at the anode during operation of the tube. Efiicientoperation of such a tube for generating or amplifying ultra-short Waves likewise requires that the length of the electrical circuits traversed by the ultra-short current shall be reduced to relatively small Values, and the stray capacitance to ground and between portions of the circuit should be reduced to the minimum possible value. Because of the difficulties arisingfrom, straycapacitance, it has been found that oscillation circuits comprising variable plate-condensers and inductances which are conventional inordinary radio circuits, create "difficulties and-that much more satisfactory operation for ultra-short wave work results if oscillation circuits of whatmay becalled the concentric transmission-line type are employed. Such oscillation circuits may comprise a tubular conductor having a cylindrical conductor of smaller diameter positioned along its axis, the two conductors being connected with each other by a plate at one end.-

An application Serial'No. 224,544 by Sheldon I. Rambo, filed August 12, 1938, for High frequency coupling condensers, and assigned to the .Westinghouse Electric & Manufacturing Company of East Pittsburgh, Pennsylvania, illustrates the use of an oscillation circuit of the concentric line'type in combination with an electrical discharge tube of the type which has just been described. To utilize-the concentric line as an oscillation circuit it is electrically coupled to the, anode of the electrical discharge device, and inorder to" minimize stray capacitance and other sources of ineificient operation, it is desirable to mak'e'the connection between the concentric line and theanode' of the discharge device as short and compactas is possible. In the Rambo arrangement the expedient has been resorted to of surrounding the radiating fins which cool the anode of thedischarge tube device by a dielecin the capacitorand a considerable power 1055 in the capacitor dielectric and elsewhere. Furthermore, the capacitance inherent in these large dimensions constitutes a fixed capacitance which amounts practically to a limitation on the magnitude of the highest frequency to which it is possible to tune the circuit.

In accordance with my present invention I avoid the use of radial cooling-fins on the anode of the discharge tube but instead employ the structure of the concentric line, in effect, as a cooling device to dissipate the heat set free at the tube anode.

In this way I am enabled to further decrease the linear dimensions of the entire ultra-short wave system as well as to avoid the dielectric and other losses inherent in the capacitor coupling employed in the Rambo system.

With the foregoing principles in mind, the drawing shows an electrical discharge tube I having an anode 2 comprising a copper shell forming the wall over the entire upper end of the tube. A control electrode 3 and an incandescent cathode 4 of. conventional type are located in the interior of the anode portion 2 and are sealed vacuum-tight to the lower end thereof by means of glass in a manner too well known in the art to require description. Current to heat the cathode 4 is supplied from a transformer 5 having a grounded casing and the cathode leads are grounded through two condensers 6, I near their point of entrance to the tube I. The control electrode 3 is connected to one terminal of a conventional input circuit, the other terminal of which may be grounded and this ground is connected to the grid through a condenser 8 and a resistor 9. The connections of the tube I so far described are conventional ones and may be replaced by any other suitable connections for impressing the voltage of an input circuit between the cathode 4 and the control electrode 3.

The tube I. may conveniently be mechanically supported by the concentric line structure com.- prising a grounded metallic tube II which may be aflixed to a grounded supporting frame. The tube II may have one end closed by a metal plate I2 which supports in the central axis of the tube II a cylindrical core I3. The end of the core I3, which is opposite to the plate I2, is machined out to receive with a perfect lit the anode 2 of the tube I'. Since the core I3. tightly fits the tube anode 2, it constitutes an enicient means for conducting away the heat dissipated within said anode. during operation of the tube I. Heat flows from the anode I longitudinally of the core I-3 tothe opposite end thereof which is provided with aseries of radiating vanes I4 to help in maintaining the temperature of the end plate I2 as near to that of the room as possible. Some of the heat flowing along the core I3 flows into the end plate I2- and from the latter into the tube II so that these last named elements likewise help in dissipating the heat generated within the anode of tube. I.

In order to tune the concentric line consisting of tube Il anode plate I2 and core I3, a structure comprising a collar I5, a disk l6, and an annular ring I? is arranged to slide along the core I3. Theouter diameter of the ring I! is made slightly less than the internal diameter and the tube II, as a result of which the structure I5, I6, I! is capacitively coupled to the tube II- by the annular spacing last mentioned. The collar I5 forms a tight sliding fit with the core I3 and if necessary to. maintain good electrical contact thereto, sliding brushes such as element I8 may be provided in a manner well known in the electrical art.

When the collar IE, I6, I l is displaced along the core I3, the space between the disk I5 and the end plate I2 is traversed by an electrical field and the entire arrangement constitutes a tuned oscillating circuit having an extremely low decrement. The wave length of this electrical circuit is at a maximum when the disk I5 is adjacent the end plate I2 and is at a minimum when the disk I! is adjacent the open end of the tube II.

In order to tune the concentric line just described, provision is made for sliding the collar I5 along the core I3. The adjusting arrangement comprises a rod 2I which may beef metal, or may be of some insulating material such as micarta, which is preferably of a very small diameter, and which extends through a small hole bored in the central axis of core I3. Two deep and narrow slots connecting the central hole in member I3 with its periphery extend for a considerable distance. of the length of member l3, and permit a pin 22. which is set in the end of the rod 2| and extends through holes in the collar I5 to move the. latter along the core I3 when a push or pull. is exerted on the outer end ofthe rod H.

To energize the. electrical. circuits of the tube I a source of voltage 23 is connected through a choke. coil 24 with the lower end of the rod I3.

Since most of the heat generated. in the anode 2- flows longitudinally along the. core I3, it is highly desirablethat the impedance to heat flow of the latter shall be minimized. For this reason the core I3 is preferably made of copper or some other good heat conductor and the size of its central hole and appurtenant slots is made as small aspossible. The temperature difference between the lower and the upper .end of the core I'3 may be kept to any desired low value increasing the diameter of the core I3 to the necessary diameter.

Togive a specific illustrationv of one embodiment of my invention, I have found that where the tube I was of the type sold under the trade designation WX-3005. and operated. to dissipate 150 watts of power at its anode in conjunction with a core I3 having a length of 12 inches and a diameter of 1.6 inches, the temperature difference between the upper. and lower ends of the core I3 was less than. C..with ordinary room temperatures. surrounding the apparatus. This provides a safe operating temperature for the tube I.

In accordancewith the patent statutes I have described a specific. embodiment of my invention, but-the principles thereof will be applicable in many other ways which will be evident to those skilled in the. art.

I claim as my invention:

1. In combination with an electrical discharge device adapted to transmit ultra-short radio waves and having an anode comprising a metallic portion of its wall, air-cooling means including an oscillation circuit comprising a substantially solid central core having a high heat conductivity in goodheat exchanging relation with said anode having a surrounding tubular portion connected to said core at the end remote from said discharge device by an end plate.

2. In combination with an electrical discharge device adapted to transmit ultra-short radio waves and having an anode comprising a metallic portion of its wall, air-cooling'means including an oscillation circuit comprising a substantially solid central core having a high heat conductivity in good heat exchanging relation with said anode having a surrounding tubular portion connected to said core at the end remote from said discharge device by an end plate, said oscillation circuit being provided with an annular member slidable upon said core and separated from said tubular member by an annular gap.

3. In combination with an electrical discharge device adapted to transmit ultra-short radio waves and having an anode comprising a metallic portion of its wall, air-cooling means including an oscillation circuit comprising a substantially solid central core having a high heat conductivity in good heat exchange relationship with said anode surrounded by a tubular conductor connected at one end to said core, said oscillation circuit being provided with an annular member I slidable upon said core and separated from said tubular conductor by an annular gap, and cooling vanes upon the end of said core adjacent said metal plate.

4. In combination with an electrical discharge device adapted to transmit ultra-short radio waves and having an anode comprising a metallie portion of its wall, air-cooling means including an oscillation circuit comprising a substantially solid central core having a high heat conductivity and a recess at one end accurately fitting the exterior of said anode, a metal tube surrounding said core and a metal plate at the other end of said core connecting it to said metal tube,

and means for cooling the end of said core adjacent said metal plate, said core forming the main path for flow of heat from said anode to said metal plate.

5. In combination with an electrical discharge device adapted to transmit ultra-short radio waves and having an anode comprising a metallic portion of its wall, air-cooling means including an oscillation circuit comprising a substantially solid central core having high heat-conductivity and having a recess at one end accurately fitting the exterior of said anode, a metal tube surrounding said core and a metal plate at the other end of said core connecting it to said metal tube, an annular member making a sliding fit upon said core and having an annular gap of small dimensions between its periphery and the internal surface of said tube.

JOHN A. HUTCHESON. 

